5+ Stinging Nettle Benefits + Side Effects

While stinging nettle may sound like a dangerous plant, it can be prepared into a supplement with potential benefits against inflammation, allergies, and arthritis. Although it is considered safe, stinging nettles has its risks and side effects as well.

What is Stinging Nettle?

Stinging nettle (Urtica dioica) is an herb native to parts of Europe, Africa, Asia, and North America. Civilizations as old as Ancient Greece used this plant for its medicinal properties, though our modern names for it come from the Anglo-Saxon “noedl” (needle) and the Latin “urtica” (to burn) [1, 2].

Stinging nettle has been used as a food, fabric, medicine, and cosmetics for thousands of years. Its wide array of uses includes everything from enhancing male health to easing nasal congestion [3, 4].

Touching the leaves of a wild stinging nettle can cause skin irritation. However, when processed for consumption, the nettle’s stinging hairs are crushed, cooked, or boiled in a way that eliminates their stinging abilities and makes them safe for consumption [5].

Snapshot of Stinging Nettle

Proponents:

• Reduces arthritis pain
• May relieve benign prostatic hyperplasia
• May decrease blood pressure and blood sugar
• Reduces inflammation
• Other possible benefits for testosterone, water retention, and healing

Skeptics:

• Stinging spines may cause a rash
• Rare allergic reactions to raw juice or purée
• May have dangerous drug interactions
• May worsen conditions with too much testosterone

Components

Bioactive Compounds of Leaves

Stinging nettle contains multiple bioactive compounds responsible for its health and antioxidant effects. These include [3]:

• Quercetin, an antioxidant and anti-diabetic compound [6, 7]
• Rutin, closely related to quercetin [8]
• Kaempferol, a potent anti-inflammatory compound [9]
• Quinic acid, an antioxidant and anti-inflammatory compound [10]
• Caffeic acid, another strong antioxidant [11]
• Choline, a vital nutrient with anti-inflammatory properties [12]
• Lecithin, a healthy fat that may help reduce cholesterol [13]

Bioactive Compounds of Root

Stinging nettle root has a significantly different chemical profile than the leaves, with about half the quinic acid and almost no caffeic acid by comparison. However, the roots also contain some compounds not found in the leaves, such as fatty acids, plant sterols, secoisolariciresinol, vanillin, and scopoletin [2, 14, 15].

The compounds in nettle root may protect against heart disease, affect the brain, and reduce cholesterol. The root is also particularly effective against benign prostatic hyperplasia [2, 14, 15].

Nutritional Value

Fresh stinging nettle plants contains many valuable vitamins and nutrients, including provitamin A, vitamin B1, vitamin K, potassium, calcium, and iron. It also contains oxalates, which will bind to these minerals and reduce their absorption [3].

Mechanism of Action

Stinging nettle is an antioxidant: it blocks the oxidation of fats, linoleic acid, deoxyribose, and muscle proteins, thereby protecting many tissues from oxidative stress [2].

Stinging nettle reduces inflammatory cytokine release and reduces inflammatory biomarkers like TNF-a, IL-1, IL-6, and hs-CRP. It also interferes with the way the body sends pain signals and decreases the sensation of pain [16, 17, 18, 19].

These anti-inflammatory effects appear to also help allergies, reduce nasal congestion, help with arthritis, and more [2].

Why Touching a Wild Nettle Hurts

If you see a stinging nettle plant growing wild, don’t touch it without gloves! Nettle leaves and stems are covered with tiny, stinging hairs called trichomes, which will pierce your skin and inject an irritating fluid containing formic acid, histamine, acetylcholine, and serotonin. Histamine is an inflammatory compound that will make your skin red and irritated, and formic acid is the chemical that causes pain from ant and bee stings [2].

Proper preparation of stinging nettle leaves deactivates the formic acid. A high-quality stinging nettle leaf product will not contain anywhere near enough formic acid to cause concern [2].

Health Benefits of Stinging Nettle

Stinging nettle supplements have not been approved by the FDA for medical use and generally lack solid clinical research. Regulations set manufacturing standards for them but don’t guarantee that they’re safe or effective. Speak with your doctor before supplementing.

Possibly Effective For

1) Arthritis and Pain

Stinging nettle’s anti-inflammatory properties could potentially help relieve arthritis symptoms. A combination of stinging nettle leaf extract and devil’s claw significantly reduced symptoms of arthritis compared to a placebo in a 12-week study of 92 arthritis patients [20].

These arthritis-relieving properties may be due to nettle’s ability to inhibit the activation of a protein called NF-κB, which would otherwise increase the production of inflammatory compounds. NF-κB is often overactive in people with arthritis [21, 22].

Stinging nettle is often used by traditional practitioners. Urtication, also known as ‘flogging with nettles,’ is a technique where users apply raw, unprocessed stinging nettle leaves or stems to the body to generate inflammation. This has been used since Ancient Roman times for relieving chronic rheumatism, but researchers have only just begun to investigate its effectiveness [23].

There is also evidence that using stinging nettle leaves topically can help relieve pain in those with:

• Lower back pain [24]
• Thumb pain [5]
• Knee pain [25]

Insufficient Evidence For

The following purported benefits are only supported by limited, low-quality clinical studies. There is insufficient evidence to support the use of stinging nettle for any of the below-listed uses. Remember to speak with a doctor before using stinging nettle, and never use it in place of something your doctor recommends or prescribes.

2) Allergies (Hay Fever)

Taking stinging nettle leaf extracts help decrease allergies. Scientists believe this may be due to the plant’s ability to reduce histamine production and inflammatory markers.

Both freeze-dried nettle leaves and nettle tea may also help with nasal allergies and allergic reactions [26, 27].

In one study, 57% of patients were said to have rated nettle as ‘effective’ in helping allergies, with 48% even saying nettle was more effective than allergy medications they had used previously [28].

However, stinging nettle also contains histamine – especially the leaves and hairs. More research is required to fully understand how this plant can reduce mast cell activation despite containing histamine. Many of its other bioactive compounds likely act together to achieve an altogether allergy-relieving effect [26, 2].

3) Benign Prostatic Hyperplasia (BPH)

Benign prostatic hyperplasia (BPH) is a condition wherein the prostate gland becomes enlarged, usually due to age. This can cause difficulty urinating and various other symptoms, including sexual dysfunction [29, 30].

Stinging nettle root extracts are among the most popular herbal remedies used to ease the symptoms of enlarged prostates, though the evidence is still considered insufficient for medical use [31, 32].

A review of several studies showed that stinging nettle root extract effectively improves the symptoms of an enlarged prostate, with a low risk of negative effects or toxicity [1].

In a study of 246 BPH patients, a special extract of stinging nettle safely and effectively reduced the adverse effects of prostate enlargement when compared to placebo [33].

In another 6-month study of 558 people, stinging nettle roots significantly improved multiple measures of prostate health, including [34]:

• Relief of lower urinary tract
• Maximum urinary flow rate
• Residual urine volume
• Prostate size
• International Prostate Symptom Score

Another study combined stinging nettle and saw palmetto extract. It was as effective as and better tolerated than the prescription drug finasteride, which is used to treat enlarged prostates [35].

The inhibiting effects of stinging nettle root extracts were also demonstrated in rats and mice with induced large prostates [36, 37].

Note that stinging nettle root has been significantly more effective than leaf or stem in studies of people with BPH. This may be due to high lignan content, which the leaves don’t contain.

Larger and more robust studies with standardized extracts and preparations will be required to determine the role of stinging nettle in BPH.

4) Blood Sugar

Stinging nettle leaves and stems – but not roots – may help decrease blood sugar. Chemicals in nettle leaves appear to trigger the release of insulin and other compounds that reduce blood sugar [38, 39].

In a study of 92 subjects, stinging nettle extract decreased fasting blood sugar levels and other blood sugar levels when compared with the placebo [40].

Stinging nettle also decreased blood sugar and increased insulin in rat studies [41, 39].

A leaf extract of stinging nettle improved blood sugar balance in mice and helped with insulin resistance, which delayed the onset of type 2 diabetes [42].

5) Inflammation

Stinging nettle leaf extracts may block inflammatory markers (TNF-a, IL-1, IL-6, NF-kB, etc.) and reduce inflammation in the body [16, 17, 21].

In a study of 37 arthritis patients, combining stinging nettle tea with diclofenac (a non-steroidal anti-inflammatory drug or NSAID) enhanced the drug’s anti-inflammatory effects [43].

In mouse immune cells (macrophages), stinging nettle extract was as effective at reducing inflammation as celastrol from thunder god vine. Both were powerful antioxidants and anti-inflammatories [44].

Nettle also inhibited human leukocyte elastase, which is known to increase inflammation [1, 45, 46].

Animal & Cell Research (Lacking Evidence)

No clinical evidence supports the use of stinging nettle for any of the conditions listed in this section. Below is a summary of the existing animal and cell-based research, which should guide further investigational efforts. However, the studies listed below should not be interpreted as supportive of any health benefit.

6) Free Testosterone

Free testosterone is the available blood testosterone, not bound to sex hormone binding globulin, or SHBG. The less testosterone that’s bound to SHBG, the more free testosterone is available for the body to use. Testosterone bound to SHBG is unusable to the body [47].

Stinging nettle roots contain substances called ligans, which bind to SHBG. This reduces the amount of SHBG that can bind testosterone; hence, while nettle does not increase total testosterone in the blood, it may increase available testosterone. Bodybuilders have traditionally used similar plant substances to increase free testosterone [48, 34, 49].

Multiple cell studies have shown that lignans from stinging nettle roots reduced SHBG binding to testosterone [50, 51, 49].

There is also evidence that stinging nettle blocks the conversion of testosterone into estrogen, an effect that may be increased with the addition of saw palmetto. This combination appears to act on an enzyme called aromatase, which converts testosterone to estrogen, but does not affect testosterone receptors [1].

7) Blood Pressure

Stinging nettle stems and leaves may reduce blood pressure, but they could also increase the risk of blood pressure dropping too low. In rats, stinging nettle lowered blood pressure by increasing the amount of salt that the kidneys filtered out of the blood [52].

Stinging nettle can also lower blood pressure by triggering the release of nitric oxide, which causes blood vessels to widen [53, 54].

8) Water Retention

Diuretics, sometimes called water pills, are medications that increase urine production. They can help remove excess sodium and water from the body. In animal studies, stinging nettle increased urine flow and acted as a diuretic [52, 55].

Proper use of diuretics can help with various health complications by [56, 57]:

• Decreasing blood pressure
• Compensating for poor kidney function
• Reducing bloating

9) Wound Healing

In rats, stinging nettle leaf extracts improved the quality of healing of second-degree burns in rats when applied to their skin. It accelerated healing and reduced scarring more effectively than conventional methods (vaseline and silver sulfadiazine) [58].

A very limited human study of eight experimental burns using a gel with stinging nettle leaf extracts with arnica extracts seems to support this benefit [59].

Limitations and Caveats

Although there is a large body of promising research, caution should always be used when extrapolated the results of animal studies to humans. Also, as with any supplement, care should be used in taking it.

A few studies have demonstrated that different parts of the stinging nettle plant contain different chemical compounds and may have completely different effects. Some research that claims that nettle extracts either do or do not have certain benefits may not have investigated each part of the plant, each extract, or even the ideal extract for the job.

Side Effects & Safety

Although certain applications require the leaves to be applied directly to the skin, we do not recommend touching a wild stinging nettle with your bare hands. The formic acid and histamine in the sharp “hairs” on the nettle’s surface will likely cause a red, lumpy rash. In addition, some people may experience an allergic reaction to raw puréed nettle or nettle juice [2].

Stinging nettle may increase free testosterone and may, therefore, worsen any health conditions characterized by too much testosterone, such as polycystic ovarian syndrome (PCOS) [60].

Due to possible contractions of the uterus, stinging nettle may be unsafe to take during pregnancy. Contractions of the uterus can cause a miscarriage or cause women to go into early labor. There are no available studies about the effects of stinging nettle on nursing infants, so it is recommended to consult your doctor if you are considering taking it while breastfeeding [5, 61].

Stinging nettle is sometimes used to increase milk production in nursing mothers, but no safety data exists; we therefore caution against using stinging nettle while breastfeeding [5, 61].

Drug Interactions

Combining stinging nettle with hypertension and diabetes drugs may cause your blood pressure and blood sugar to become too low [54, 41].

The active compounds in stinging nettle may block metabolic enzymes in the CYP1A family, thereby increasing the effects of any drugs broken down by these enzymes. In rats, this effect has been demonstrated with melatonin; other drugs that may be affected include caffeine, warfarin, and many others [62, 63].

By the same token, stinging nettle can increase the beneficial effects of non-steroidal anti-inflammatory drugs (NSAIDs) like ibuprofen (Advil) and naproxen (Aleve) [64, 43].

Talk to your doctor before supplementing with stinging nettle to prevent adverse events or unexpected interactions.

Supplementation & Dosage

Forms of Stinging Nettle

Stinging nettle is usually available in the following forms:

• Tea
• Capsules (leaf or root extract)
• Tinctures (extract dissolved in alcohol)
• Loose leaves
• Dried roots
• Cream or gel (for arthritis and pain)

If collected and processed carefully, wild stinging nettle can also be gathered and cooked into many recipes. Look for instructions from experts before attempting to harvest nettle yourself.

Always check the label to make sure which part of the plant was used to make a given product.

Dosage

There is no safe and effective dose of stinging nettle for any medical purpose because no sufficiently powerful study has been conducted to find one. That being said, many studies have found an association between certain doses of nettle and beneficial effects.

A dosage of 450 mg of dry stinging nettle root extract per day is associated with beneficial effects for benign prostatic hyperplasia. Many commercial root supplements come in 250 mg or 500 mg capsules [33].

Increasing free testosterone is dose-dependent. A root tincture with a concentration of 0.6 mg/ml significantly blocked testosterone binding to SHBG; at a concentration of 10 mg/ml, binding was inhibited completely [65].

Commercial leaf extracts sometimes come with recommendations of between 275 mg and 2 g of their product per day; note that the quality and content of these extracts is likely variable. Raw stinging nettle leaf, cut from the live plant, significantly reduces pain when applied to directly to an arthritic joint for thirty seconds, once per day [66].